Check valve for a vacuum pump



June 20, 1967 J. A. LE BLANC, JR 3,326,456

CHECK VALVE FOR A VACUUM PUMP Filed Sept. 13, 1965 2 Sheets-Sheet l INVENTOR JOSEPH A. LEBLANcJR.

June 20, 1967 J, A LE BLANCY JR 3,326,456

CHECK VALVE FOR A VACUUM PUMP United States Patent 3,326,456 CHECK VALVE FOR A VACUUM PUMP Joseph A. Le Blane, .lr., Chicago, llL, assignor to Precision Scientific Company, Chicago, llll., a corporation of Illinois Filed Sept. 113, i965, Ser. No. 486,868 6 Claims. ((Il. ZSii-Zili) The present invention relates generally to vacuum pumps and more particularly to an improved vacuum pump check valve.

One of the difficulties encountered in the past in the design of lubricating systems for vacuum pumps has been the excessive noise and clatter caused by the operation of the pump valves which regulate the flow of the lubricant, and those skilled in the art have even experienced difiiculty in recognizing with certainty the cause of this objectionable noise. In the conventional flutter valve used in vacuum pumps, it appears that the exhaust outlet is actually sealed off from the oil supply between flutters so that a void is formed within the exhaust chamber of the pumping unit. Then as the pump rotor sweeps the oil within the rotor chamber upwardly toward the exhaust hole, the mass of oil is slammed up against the valve member causing a banging noise.

Some continuously open flutter valves also have been use in the past, but such valves have not been free from noise and have been difficult to assemble and maintain accurately in position. Such valves have been formed by placing a valve plate a small distance away from the exhaust port so that the pressure of the main oil supply bends the end of the plate down over a major portion of the opening but leaves a small fraction of the opening uncovered to allow for a continuous flow of oil through the exhaust port. Since the degree of bending in the plate member will vary with different pressures, and due to the tendency of viscous oil to collect at the edge of the uncovered portion of the opening, such valves have presented difiicult mechanical problems in their assembly and maintenance.

An object of the present invention is to provide a vacuum pump check valve which is easily manufactured and assembled and runs efliciently and quietly without the characteristic noise of conventional pump valves.

Another object of the invention is to provide a vacuum pump check valve which is maintained continuously open but provides an efficient control and resistance to the how of lubricant without any criticality in the spacing of the valve plate or the pressures to which it is subjected.

A further object is to provide a vacuum pump check valve which is continuously open to permit a controlled flow of lubricant into the pumping chamber so as to prevent the existence of a void in the outlet port and the objectionable noises resulting therefrom. It is a related object to provide a check valve which is continuously open and permits an increased flow of oil as the pressure differential increases between the pumping chamber and the oil chamber.

Still another object is to provide a vacuum pump check valve which operates in a manner so as to prevent the collection of dirt and viscous material which may clog the valve opening.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and by reference to the drawings in which:

FIGURE 1 is a side elevational view of a single stage vane type vacuum pump in which the present invention is incorporated;

FIG. 2 is a perspective view of the check valve constructed in accordance with the present invention;

FIG. 3 is a. section view taken along line 3-3 in FIG. 1;

FIG. 4 is a section taken along line 4-4 in FIG. 3;

FIG. 5 is a top view of the vacuum pump;

FIG. 6 is a section view taken along line 66 in FIG. 3; and

FIG. 7a-c is a series of stop motion views showing the operation of the check valve when pumping air.

While the invention will be described in connection with a preferred embodiment it will be understood that I do not intend to limit the invention to such embodiment, but intend to cover the alternative and equivalent constructions which may be included within the spirit and scope of the appended claims.

Turning now to the drawings, the check valve is shown included in a single stage rotary vane type vacuum pump for which it is found to be well suited. However, no attempt has been made to limit the invention to such a preferred construction since such valves may also be employed in other types of vacuum pumps. In the pump shown, it may be noted in FIGS. 3 and 4- that the housing includes an end member 10 which seats a cup-shaped enclosure 11 having a flange secured to the end member 14? by suitable screws 12. Mounted on the top of the end member 10 is an inlet port 20. In the top of the housing 11 is an outlet aperture 21 and a vent cap 22 of flat disc shape.

As is usual in vacuum pumps, the inlet port 26 is connected to the system to be evacuated, and upon driving of the pump by a motor, the air or gas withdrawn from the system is discharged from under the vent cap. In the following discussion it will be assumed that air is being pumped.

The internal construction of the pump is shown particularly in FIGS. 3 and 4. Extending longitudinally through the pump is a shaft 30, one end of which is journaled in the end member 10 and the other end of which is journaled in a hearing or end plate 31. In order to hold the end plate 31 in a fixed position within the enclosure 11, a plurality of bolts 31a are passed through spaced slots in the periphery of the end plate 31 into threading engagement with the end member 10. A seal indicated at 32 is interposed between the shaft 30 and the enclosure 11 to prevent escape of the sealing and lubricating oil which is conventionally contained within the enclosure 11.

Surrounding the central portion of the shaft 30 between the end member 19 and the plate 31 is the pumping unit 40 having a stator 41 in the form of a ring made of cast iron or the like having an irregular outline and a circular opening 42 which is eccentric with respect to the shaft 30. Mounted within the opening 42 is a rotor 43 in the form of a metal disc having accurately ground end faces, the rotor being in contact with the stator at a terminal region 43a. The rotor 43 is secured to the shaft 30 by a key 44 and is slotted to accommodate radially extending vanes 49 which are spring pressed outwardly against the stator by means of a coil spring 47.

For the purpose of admitting air from the inlet 29 into the space between the rotor and stator, an opening '50 is provided in the wall of the end member 1.0. Moreover, for conducting the air, the edges of the opening 42 are grooved or relieved to provide inlet ports 51, 52 which are interconnected by an axially extending passage '53 (FIG. 4). For discharging the air from the pumping chamber, outlet ports are formed in the stator of similar thickness and symmetrically located on the opposite sides of the region of contact 43a between the stator and rotor. The outlet ports are indicated at 55, 56 and are interconnected by a passage 57.

Although the operating cycle of a vane type vacuum pump is well known to those familiar with the vacuum pump art, it may be helpful to briefly review the operation of such pumps in a general fashion. As the rotor 43 is rotated eccentrically within the rotor chamber formed by the stator 41, the rotor is in continuous contact with the stator at the region of contact 43a and the two vanes 49 move progressively around the periphery of the rotor chamber. During the course of each revolution, air is drawn into the rotor chamber through the inlet ports 51, 52 and transferred to the outlet ports 55, 56 where it is discharged from the pump to the atmosphere. For the purpose of lubricating the moving parts and to form a seal against the leakage of air from the atmosphere to the vacuum side of the pump, a small amount of oil is continuously maintained within the rotor chamber. This lubricating and sealing oil flows between the rotor chamber and the oil supply chamber around the stator 41 through an exhaust port 58, with the oil flow being controlled by a check valve 59.

In accordance with the present invention a novel check valve of resilient material is provided at the exhaust port which in its unstressed condition lies flatly against a land portion around the port and has an opening therein which varies in size according to the pressure differential across the valve plate so as to permit a continuous flow of oil through the port. Thus, in the illustrative embodiment, the check valve com-prises a plate 60 which covers the exhaust port 58 and is mounted at one end by a machine screw 61 or the like. The plate in its unstressed condition lies flatly against the land 62. that surrounds the mouth 63 of the exhaust port which may be desirably formed by the chamfering indicated at 63.

In order to form a tight oil seal around the periphery of the port 53, the plate 60 completely covers the outer end of the port as well as a substantial portion of the land 62. surrounding the port, with the mounting screw 61 holding the plate in tight bearing engagement with the land 62. To permit the controlled passage of lubricating and sealing oil through the check valve, a slit 64 is formed in the free end of the plate so that the opposed edges 64a and 64b formed by the slit define an elongated narrow opening which starts at the free end of the plate and extends diametrically across the port. The slit 64 continues a short distance beyond the port toward the stationary end anchored by the screw 61 and terminates in a relief slot 65 provided to prevent further splitting of the spring plate during operation thereof. It will be appreciated that the check valve formed by the split plate 60 is continuously open to permit a continuous flow of oil therethrough, but

the size of the opening (and thus the oil flow rate) may be varied by deflecting the opposed edges 64a and 64b into or away from the port 58. In actual operation of the pump, these deflections are controlled by the pressure differential across the plate 60, as will be described in more detail below.

In the illustrative embodiment of the check valve described above, the plate 60 is preferably formed of blue flat spring steel. The slit opening is generally within the range of 0.0005 to 0.002 inch, depending mainly upon the amount of oil necessary to lubricate the pump and the size of the exhaust port. While the operative phenomenon of the inventive check valve are the subject of continuing investigation, nevertheless, for further understanding of the invention, reference may be made to a series of stop motion views in FIG. 7 which illustrate the operation of the valve during various portions of the pumping cycle. Thus referring to FIG. 7a, the pressure in the port 58 is below atmospheric pressure when the active zone 49 of the pump is at a position farthest removed from the port 58. The atmospheric pressure above the plate 60 then causes the opposed edges 64a and 64b formed by the slit 64 to deflect downward. Consequently, oil is drawn through the slit opening 64 into the port and into cont-act with the rotor with the rate of flow being controlled by the resistance of the plate. The oil which is drawn in effectively seals the rotor to the stator so that there is no leakage of air from the outlet to the inlet. As the cycle continues, the vane in the rotor causes the air between the rotor and the stator to be compressed so that pressure at the port 58 is increased causing the opposed edges of the plate to deflect upwardly. The point is reached as shown in FIG. 71) at which the opposed edges of the plate are horizontally aligned with each other; at this point, the valve resistance is at a maximum, but it still remains open due to the narrow opening of the slit. The vane then continues to sweep the oil within the pumping chamber upwardly toward the port 58 until the pressure beneath the valve member exceeds that above so that the opposed edges 64a and 64b of the slit are deflected upwardly, as shown in FIG. 70, permitting oil to be forced through the plate at a faster rate. As the vane passes the outlet port, 55, 56 the pressure in the port is decreased again and the opposed edges return to their unstressed position.

It is found that in employing a valve of the above type a number of important advantages are derived. The valve of the present invention has been found to operate efiiciently and quietly without the loud noise and clatter which have characterized vacuum pumps in the past. The improved operation has resulted from maintaining the valve continuously open throughout the pumping process regardless of the pressures across the valve plate. The size of the opening in the valve, however, varies at different stages of the pumping cycle to provide the most efl icient control of the oil flow. Since the valve is continuously open, the exhaust port is never sealed off to form a void as was often the case with conventional non-split flutter valves.

Furthermore, the valve of the present invention is easily assembled and may be operated efliciently over long periods without noticeable wear and without adjustment or maintenance. Since the valve plate is fastened so that while in an unstressed condition the free end of the plate lies flatly against the land surrounding the exhaust port, there is no critical spacing required as is the case with open flutter valves used in the past which required accurate placement of the valve a distance from the exhaust port as well as frequent adjustment.

Still another advantage of the valve of the present invention is that the fluttering of the opposed edges of the valve plate prevents the collection of dirt and viscous material in the valve opening, which is a defect often encountered with valves in which accurate spacing is required.

I claim as my invention:

1. In a vacuum pump having a frame, a pump unit in said frame having at least one pump chamber, an inlet port and an exhaust port surrounded by a land portion, said pump unit being adapted for immersion in an oil supply, a continuously-opened check valve comprised of a plate of resilient material covering said exhaust port, said plate being secured at one end and when in an unstressed condition lying flatly against said land portion of the exhaust port, said plate having a slit therein centered with respect to the exhaust port with the opposed edges formed by said slit spaced apart to permit a controlled flow of oil, said opposed edges being capable of deflecting into the exhaust port when pressure is exerted on the plate by the oil supply and capable of deflecting away from the exhaust port when oil within the pump chamber is forced by the pump unit against the plate whereby the flow of oil through said slit is automatically controlled in response to the pressure differential across the check valve, the peripheral portion of the plate away from said slit remaining flatly against said land portion of the exhaust port during the deflection of the opposed edges into and away from the exhaust port.

2. In a vacuum pump having a frame, a pump unit in said frame having at least one pump chamber, an inlet port and an exhaust port surrounded by a land portion, said pump unit being adapted for immersion in an oil supply, a continuously-opened check valve comprised of a plate of resilient material covering said exhaust port, said plate being mounted so thatwhen in an unstressed condition the plate lies flatly against the land portion of said exhaust port, said plate having a narrow opening for permitting a continuous flow of oil through the exhaust port, the edges on the opposite sides of the opening being capable of deflecting into the exhaust port when pressure is exerted on the plate by the oil supply and capable of deflecting away from the exhaust port when oil within the pump chamber is forced by the pump unit against the plate whereby the flow of oil through said narrow opening is automatically controlled in response to the pressure differential across the check valve, the peripheral portions of the plate away from the narrow opening remaining flatly against said land portion of the exhaust port during the deflection of the opposed edges into and away from the exhaust port.

3. In a vacuum pump having a frame, a pump unit in said frame having at least one pump chamber, an inlet port and an exhaust port surrounded by a land portion, a continuously-opened check valve comprised of a plate of spring material covering said exhaust port, said plate being mounted at one end thereof so that when in an unstressed condition the plate lies flatly against the land portion of said exhaust port, the other end thereof being free, said plate having a narrow opening therein centered with respect to the exhaust port beginning at the free end of the plate and extending a distance past the exhaust port, the opposed edges formed by said narrow opening being spaced apart to permit a controlled flow of oil, said opposed edges being capable of deflecting to vary the size of the opening according to variations in the pressure difierential across the plate, the peripheral portions of the plate away from the narrow opening remaining flatly against said land portion of the exhaust port during the deflection of the opposed edges.

4. In a vacuum pump having a frame, a pump unit in said frame having at least one pump chamber, an inlet port and an exhaust port surrounded by a land portion, said pump unit being adapted for immersion in an oil supply, a continuouslyopened check valve comprised of a plate of spring material covering said exhaust port, said plate being secured at one end, the other end thereof being free, and when in an unstressed condition lying flatly against said land portion of the exhaust port, said plate having a slit therein centered with respect to the exhaust port beginning at the free end of the plate ex tending a distance past the exhaust port and terminating in a relief, the opposed edges formed by said sli-t being spaced apart to permit a controlled flow of oil, said 0pposed edges being capable of deflecting into the exhaust port when pressure is exerted on the plate by the oil supply and capable of deflecting away from the exhaust port when oil within the pump chamber is forced by the pump unit against the plate, the peripheral portions of the plate away from said slit remaining flatly against said land portion of the exhaust port during the deflection of the opposed edges into and away from the exhaust port.

5. In a vacuum pump having a frame and a pump unit in said frame having at least one pump chamber, an inlet port and an exhaust port surrounded by a land portion, the improvement that comprises a continuouslyopened check valve comprising a leaf spring covering said exhaust port, one end of the leaf spring being rigidly anchored and the other end thereof being free, the leaf spring lying in flat engagement with the land portion so as to form an oil seal around the periphery of the exhaust port, the free end of the spring having formed therein a narrow opening for permitting a continuous flow of oil throughthe exhaust port, portions of the spring on opposite sides of the narrow opening being adapted to vary the size of the opening according to variations in the pressure differential across the spring.

6. The improvement, as claimed in claim 5, wherein the portions of the spring on opposite sides of the narrow opening are capable of being deflected into the exhaust port when pressure is greater outside the pump unit and being capable of deflecting away from the exhaust portion when pressure is greater within the pump unit.

References Cited UNITED STATES PATENTS 1,031,801 7/1912 Madden 230-152 1,428,399 9/1922 Schilling 137-525.1 1,949,710 3/ 1934 Dubrovin 230-205 2,998,826 9/1961 Sadler 137-5251 ROBERT M. WALKER, Primary Examiner. 

1. IN A VACUUM PUMP HAVING A FRAME, A PUMP UNIT IN SAID FRAME HAVING AT LEAST ONE PUMP CHAMBER, AND INLET PORT AND AN EXHAUST PORT SURROUNDED BY A LAND POTION, SAID PUMP UNIT BEING ADAPTED FOR IMMERSION IN AN OIL SUPPLY, A CONTINUOUSLY-OPENED CHECK VALVE COMPRISED OF A PLATE OF RESILIENT MATERIAL COVERING SAID EXHAUST PORT, SAID PLATE BEING SECURED AT ONE END AND WHEN IN AN UNSTRESSED CONDITION LYING FLATLY AGAINST SAID LAND PORTION OF THE EXHAUST PORT, SAID PLATE HAVING A SLIT THEREIN CENTERED WITH RESPECT TO THE EXHAUST PORT WITH THE OPPOSED EDGES FORMED BY SAID SLIT SPACED APART TO PERMIT A CONTROLLED FLOW OF OIL, SAID OPPOSED EDGES BEING CAPABLE OF DEFLECTING INTO THE EXHAUST PORT WHEN PRESSURE IS EXERTED ON THE PLATE BY THE OIL SUPPLY AND CAPABLE OF DEFLECTING AWAY FROM THE EXHAUST PORT WHEN OIL WITHIN THE PUMP CHAMBER IS FORCED BY THE PUMP UNIT AGAINST THE PLATE WHEREBY THE FLOW OF OIL THROUGH SAID SLIT IS AUTOMATICALLY CONTROLLED IN RESPONSE TO THE PRESSURE DIFFERENTIAL ACROSS THE CHECK VALVE, THE PERIPHERAL PORTION OF THE PLATE AWAY FROM SAID SLIT REMAINING FLATLY AGAINST SAID LAND PORTION OF THE EXHAUST PORT DURING THE DEFLECTION OF THE OPPOSED EDGES INTO AND AWAY FROM THE EXHAUST PORT. 